Device for inspecting the straightness of bores



Dec. 16, 1958 w. E. KELLER El'AL 2,864,230

DEVICE FOR INSPECTING THE STRAIGHTNESS OF BORES Filed April 4, 1956 5 Sheets-Sheet 1 1 III! I 1/ I P l INVENTORJ;

Wi11iunLE.Ka11er Norman E. Ki: flwell DDLHJJDE F. Olive r Dec. 16, 1958 w. E. KELLER ETAL DEVICE FOR INSPECTING THE STRAIGHTNESS OF BORES Filed April 4, 1956 5 Sheets-Sheet 2 IN VEN TOR), Willi um E Keller N n rmn'n E- Ki dwell Douglas IE. Elliver BY 9W2 M 9 Q- 4/- Dec. 16, 1958 w. E. KELLER ETAL 2,864,280

DEVICE FOR INSPECTING THE STRAIGHTNESS OF BORES IN VEN TORS, Willi 11m E Kalle-P Norman. E Kir'iwell llnt glus IELUJivEr H7 7012 MET- W. E. KELLER ETAL Dec. 16, 1958 DEVICE FOR INSPECTING THE STRAIGHTNESS OF BORES Filed April 4, 1956 5 Sheets-Sheet 4 INVENTORJ, WilliumE- Kalle r Nczrmnn E Kidwe11 Douglas F Cl1iver id-Mau- Dec. 16, 1958 w. E. KELLER ETAL 5 DEVICE FOR INSFECTING THE STRAIGHTNESS OF BORES Filed April 4, 1956 5 Sheets-Sheet 5 l l l INVENTORS, WillinmE- K 211E I Norman E Kiaw'ell llcauglus F. Uliver H77ORNEYS,

2,864,280 Patented Dec. 16, 1958 DEVICE FOR INSPECTING THE STRAIGHTNESS F BORES William E. Keller, West Warren, Mass, Norman E. Kidwell, Windsor Locks, Conn., and Douglas Ford Oliver, Dearhorn, Mich, assignors to the United States of America as represented by the Secretary of the Army Application April 4, 1956, Serial No. 576,224

4 Claims. or. 88-14) This invention relates to means for checking the stra ghtness of bores and pertains more particularly to a device which checks, measures and records the longitudinal contours of the bore of a firearm barrel and which may be used in direct conjunction with a barrel straightening machine.

Various means have been devised for checking and measuring the straightness of gun barrels. One commonly used in the production lines of barrel manufacturers is referred to as line straightening. In this method, a straight reference line is reflected along the longitudinal surface of the bore. If the bore is not straight, the image of the line will be wavy. Through experience an operator can approximate by the amount and position of waviness where and how much to straighten the barrel. This method obviously requires considerable experience on the part of the operator and the results are only qualitative as the amount of bend in the barrel is not measurable hereby and only through long experience can the position of the bend be located.

Another method commonly used in production lines utilizes a straight rod of fixed length and diameter which is passed through the bore of the barrel. If the rod passes through the barrel without binding, the barrel is considered to be straight. If the rod binds, the barrel is considered to be bent. The tolerances of the bend are set by fixing the diameter and length of the rod. This method however is not satisfactory as the rod may be bent in handling and, therefore, give erroneous results. The force exerted on the rod in passing it through the barrel may also affect the result as a large enough force will cause the rod to bend inside the barrel bore and assume bore shape. It is also obvious that any burr or roughness in the bore surface would give a faulty indication.

Another method, used to a considerable extent by German ordnance manufacturers, utilizes the measurement of relative bore slope for determining the deviation of a barrel bore from axial alignment. By this method a plug provided with a surface mirror on the front end is inserted into the bore of the barrel and the barrel then drawn over it. An autocollimator projects a cross onto the mirror surface of the plug and is reflected therefrom onto a screen. As the barrel is drawn over the plug, the plug assumes a position in the bore in accordance with the slope of the section of the barrel in which the plug lies. The light beam consequently is reflected onto the screen at an angle which depends upon the slope of the barrel section. The slopes of the bore is determined mathematically by the position of the reflected cross relative to a fixed, predetermined reference on the screen, taking into consideration the degree of magnification, or by calibrated divisions on the screen.

In this method however the result gives only an indication of the angle of slope of the bend and does not directly measure the deviation which is greatest at the apex of the bend where the slope is 0.

It is an object of this invention to provide a device .which measures directly the deviation of a bend in the bore of a barrel and which may be used in direct conjunction with a bore straightening machine.

It is another object of this invention to provide a device which checks deviations in a barrel bore by optical means and which measures and graphically records the deviations by electrical means.

It is still another object of this invention to provide optical means which indicates any radial deviations of a bore from axial alignment and is unresponsive to longitudinal slope in the bore alone.

It is a further object of this invention to provide a device. for measuring deviation of a barrel bore from axial alignment at the operating center of a barrel straightening machine.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings in which:

Fig. 1 is a side view showing the bore checking device of this invention mounted to a bore straightening machine;

Fig. 2 is an enlarged partially cross-sectioned side view showing the rod and prism plug in position within the bore of the barrel;

Fig. 3 is a schematic view of the optical system of the device;

Fig. 4 is an enlarged perspective view of the recording portion of the device;

Fig. 5 is a schematic view of the optical system showing how angular displacement of the prism, without vertical displacement of the apex, does not affect the path of the reflected beam;

Fig. 6 is a view similar to Fig. 5 but showing how the path of the reflected beam is affected by vertical displacement of the prism apex;

Fig. 7 is an enlarged, exploded view of the rod and plug assembly;

Fig. 8 is an enlarged partially cross-sectioned view of the rod and plug assembly;

Fig. 9 is an enlarged end view of the beam splitting disc showing the reflected beam centered with the transparencies;

Fig. 10 is a schematic view showing the continuous passage of light through the transparencies of the beam splitting disc when the reflected ray is centered with the transparencies;

Fig. 11 is similar to Fig. 9 but showing the reflected beam away from the center of the transparencies;

Fig. 12 is similar to Fig. 10 but showing the interrupted passage of the reflected beam through one pair of the transparencies in the beam splitting disc when the reflected beam is off center; and

Fig. 13 is a schematic view of the electrical system of the device.

Shown in the figures is a bore straightening machine comprised of a carriage 12 which is movable along longitudinal ways 14 on a base 16. Carriage 12 is provided with a pair of spaced hollow centers 18 arranged to support a barrel 20 therebetween and permit axial access to bore 22 of such barrel from either end thereof.

Mounted to base 16 is a hydraulic press 23 having a ram 24 which is movable downwardly against barrel 20 when mounted between centers 18. Projecting upwardly from base 16 so that barrel 20 will pass thereover in close relationship during movement of carriage 12 is a pair of anvils 26 which are spaced equidistantly on each side of ram 24. Whereby, operation of press 23 moves ram 24 against barrel 20 between anvils 26 to bend the barrel at such section.

Mounted to base 16 so as to be movable as by hydraulie means into one end of bore 22 is a rod 28 which is 3 secured against rotation. Acylindricalplug .isjoined to the end of rod 28 which .is insertable into bore 22 by a hinged connection which permits vertical displacement .of such plug from a predetermined reference position by any vertical deviation in here 22. Provided adjacent the ends of plug 30 are annular rectangular grooves 32 in each of which there is received a compressible split ring 34. Rings 34 are secured to the plug by pins 36 and thereby maintain plug 30 in resilient contact with the surface of bore 22 during passage therethrough to transfer to such plug any vertical angularity present in the bore.

Extending axially into plug 30 from the free end thereof is a well 38 in which there is securely mounted as by wax means a prism 40, Prism 40 is of roof type and is provided at the inner end with a pair of plane reflecting surfaces 42which are disposed at right angles to each other and meet to form an apex 44. Prism 40 is mounted in plug 30 so that apex 44 is ,disposed transversely of the vertical plane of the bore straightening machine. By surfaces 42 being disposed at 90 to each other a beam of light projected along bore 22 and against one of the surfaces is reflected to the opposite one thereof and returned from such opposite surface along the bore parallel with the incident beam and spaced vertically therefrom according to the position, relative to apex 44, at which the incident beam is intercepted by such surfaces.

Provided adjacent the end of barrel 20, opposite that in which rod 28 is inserted, is a pentaprism 46, which is mounted as hereinafter described in line with the axis of bore 22, and a light source 48. Source 48 provides a light which is constant and without ripple and is disposed with pentaprism 46 in a plane which is right angular to the axis of bore 22. The faces of pentaprism 46 are arranged, as best noted in Fig. 3, so that rays from light source 48 are reflected therefrom along bore 22 to prism 40. Located between light source 48 and penta rism 46 is a condenser lens 53 and a glass metal-backed mirror 50 having a rectangular reticle 52 formed by the removal of a section of the metallic backing. As best shown in Fig. 3, reticle 52 passes a rectangular beam of light, noted at 54, from light source 48 to pentaprism 46 after the rays are straightened out by condenser lens 53. Beam 54 is reflected from prism 40, as a reflected beam 56, to pentaprism 46 and therefrom to mirror 50. As reflected beam 56 is parallelly spaced, as hereinbefore noted, from incident beam 54, such reflected beam is intercepted by the reflecting portion of mirror 50 away reticle 52 and consequently any deflection of such image,

and projects it onto a beam splitting disc 60 which is rotated by a synchronous electric motor 61 at a constant 1800 R. P. M. Disc 60 is encircled by four quarterly segmental transparencies 62 which are, as best shown by Figs. 9"and 11, concentric with the axis of the disc and are alternately disposed on opposite sides of a reference line 63. The ends of the inner and'outer transparencies 62 are radiallyalign ed and reference line 63, which is coincident with the inner walls of the outer transparencies and the outer walls of the inner transparencies, is arranged to bisect reflected beam 56 whencoincident with apredetermined reference path. Thus, when reflected beam 56 is coincident with the reference path, a portion of reflected beam 56' is passed by the transparencies 62 on both sides of reference line 63 and so photomultiplier tube 58 receives a stea'dyli'ght signal as is'shown by Figs. 9'and 10. However, when reflected beam 56 'movesaway from the reference path, reflected beam 56,, as best shown by-Figs. 11 and 12, isp'assed by only one pair of the transparencies 62, which may be, on one side or the .otherof reference line 63 depending .upon which way the reflected beam has moved. Therefore, as beam splitting disc 60 is revolving at 1800 R. P. M., photomultiplier tube 58 receives a 60-cycle signal which converts the direct currenbsupplied thereto to a 60-cycle alternating current having 'a phase which is determined by which pair of the transparencies 62 provides the signal.

Pentaprism 46 is mounted on a frame 64 which is adapted for slidable movement along the vertical plane of the bore straightening machine. Movement of pentaprism 46 isprovided by a phase-sensitive electric motor 66 which is connected by a gear train 68 to a rotary cam 70 which cooperates with a roller 72 on frame 64 for raising and lowering such pentaprism. Current for motor 66 is provided by the amplified alternating current supplied from photomultiplier tube 58 when the light signal is interrupted and the direction of such motor is controlled by the frequency phase of such alternating current. Therefore, upward and downward movements of pentaprism 46 are determined by the phase signal of beam splitting disc 60 as resulting from the position of reflected beam 56 relative to the reference path A chart 76, as of paper material, is mountable to carriage 12 so as to advance simultaneously with barrel 20 and a recording device 78 is mounted to base 16 so as to inscribe a line on such chart, as hereinafter described, while being moved by such carriage. Recording device 78 includes a servo, electrically-operated motor 79 and a threaded shaft 80 which is disposed parallel with chart 76 and is rotatable by such motor. T hreadably mounted on shaft 80 in a nonrotating traveler 82 from which there extends a stylus 84 arranged to inscribe a line on theface of chart 76 when moved with barrel 20.

The position of stylus 84 on the face of chart 76 is governed by the raising and lowering of traveler 82 by the reversible rotation of motor 79. Direction and amount of rotation of motor 79 is determined by the movement of pentaprism 46 through a conventional variable difierential transformer 86 having a movable arma ture coil 87, which is responsive to movement of such pentaprism, and a linear variable diflerential potentiometer 88 having a movable contact 89, which is responsive to movement of traveler 82. When pentaprism 46 is moved the change in the voltage signal induced in the stationary windings of transformer 86 is directly proportional to movement of coil 87. The signal is amplified by a conventional amplifier system 94 and used to drive motor 79. A matching network 92 is provided for'combining the signal from transformer 86 with that provided by potentiometer 88 so that the signal from such transformer is canceled when the required travel of stylus 84 has been reached.

Whereby, vertical movement of apex 44, during travel of plug 30 through bore 22 while barrel 20 is traversed by carriage 12, is translated by optical and photoelectric means to pentaprism 46 and movement of such pentaprism is magnified and communicated to stylus 84. Consequently, the relative position of stylus 84 indicates any deviations of bore 22. from the theoretical axis thereof directly under ram 24.

To facilitate straightening any deviation noted in bar rel 20, there is provided a suitable limiting switch (not shown) which is connected to press 23 for adjustably limiting movement of ram 24. Whereby, the operator by checking the reading on chart 76 under stylus 84, which is the record of the deviation directly below ram 24, may adjust the limiting switch to the recorded deviation and operation of the press will cause ram 24 to deflect barrel 20 the desired amount.

It is to be noted that by the device of this invention measurements are taken of the vertical displacements of apex 44 from a predetermined path, which is the theoretical axis of bore '22. Any change in angularity of the center line of plug 30 will not affect the path of deflected beam 56, as best shown in Fig. 5, provided apex 44 is not defiected vertically. Thus, the measurements recorded on chart 76 are those of the actual vertical displacement in bore 22 and not of the relative slope as produced by prior devices. Further, by apex 44 being positioned directly under ram 24 there is provided ready information for straightening barrel 20 and the barrel need not be repositioned for straightening.

From the foregoing it is clearly apparent that there is herein provided a novel means of checking and measuring radial deviations along the longitudinal contours of a bore which adds considerably to the art.

Although a particular embodiment of the invention has been described in detail herein, it is evident that many variations may be devised within the spirit and scope thereofvand the following claims are intended to include such variations.

We claim:

1. A device for checking the straightness of the bore of a tube including a light source, a pentaprism mounted for movement radial of the axis of the bore, a mirror disposed between said light source and said pentaprism, a reticle engraved in said mirror for passing a beam of light from said light source to said pentaprism for reflection therefrom along the bore, a roof prism having an apex and being movable along the bore according to the longitudinal contour thereof for returning said beam of light in a reflected beam to said pentaprism for reflection therefrom to said mirror with said reflected beam being parallel with said beam of light and variably spaced therefrom according to the radial relationship of said apex to the axis of the bore, electrical means responsive to movement of said reflected beam after being reflected from said mirror for moving said pentaprism to maintain said reflected beam along a predetermined path during movement of said roof prism in the bore, and means for recording the movement of said pentaprism.

2. A device for checking the straightness of the bore of a tube including a light source, a pentaprism mounted for movement in the vertical plane of the device and in alignment with the axis of the bore, motor means operable by a phase alternatable electric current for moving said pentaprism in opposite directions, a mirror disposed between said light source and said pentaprism, a reticle engraved in said mirror for passing a beam of light from said light source to said pentaprism for reflection therefrom along the bore, a roof prism having an apex and being movable along the bore according to the longitudinal contour thereof for returning said beam of light in a reflected beam to said pentaprism for reflection therefrom to said mirror parallel with said beam of light and variably spaced therefrom according to the radial relationship of said apex to the axis of the bore, means responsive to the position of the image of said reticle for alternating the phase of the electric current to said motor means for moving said pentaprism to maintain said refiected beam along a predetermined path during movement of said roof prism in the bore, and means for recording movement of said pentaprism.

3. A device for checking the straightness of the bore of a tube including a light source, a pentaprism mounted for movement in the vertical plane of the device adjacent one end of the bore, motor means operable by a phase alternatable electric current for moving said pentaprism in opposite directions, a mirror disposed between said light source and said pentaprism, a reticle engraved in 5 said mirror for passing a beam of light from said light source to said pentaprism for reflection therefrom at along the bore, a roof prism having an apex and being movable along the bore according to the longitudinal contour thereof for returning said beam of light in a reflected beam to said pentaprism for reflection therefrom to said mirror parallel with said beam of light and variably spaced therefrom according to the radial relationship of said apex to the axis of the bore, photoelectric means controlling the current to said motor means, a rotary beam splitting disc disposed in the path of said reflected beam between said mirror and said photoelectric means, staggered equally-spaced transparencies in said disc for controlling passage of said reflected beam to said photoelectric means and giving signals for zero electric current to said motor means when said reflected beam is coincident with a predetermined path and for a current of selected phase to said motor means for moving said pentaprism to return said reflected beam to said predetermined path when said reflected beam moves away therefrom through a deviation in the bore, and a stylus electrically responsive to movement of said pentaprism.

4. For a tube straightening machine having a carriage for traversing a tube under a press having a ram actuatable against the tube, a device for checking the straightness of the bore of the tube While being traversed under the ram including a light source, a pentaprism mounted for movement in the vertical plane of the device adjacent one end of the bore, motor means responsive to changes in the phase of a phase alternatable electric current for moving said pentaprism in opposite directions, a mirror disposed between said light source and said pentaprism, a reticle engraved in said mirror for passing a beam of light from said light source to said pentaprism for reflection therefrom along the bore, a roof prism having an apex and being movable along the bore according to the longitudinal contour thereof for returning said beam of light in a reflected beam to said pentaprism for reflection therefrom to said mirror parallel with said beam of light and variably spaced therefrom along said vertical plane according to the radial relationship of said apex to the axis of the bore, photoelectric means controlling the electric current to said motor means, a rotary beam splitting disc disposed in the path of said reflected beam between said mirror and said photoelectric means, staggered equallyspaced transparencies in said disc for controlling passage of said reflected beam to said photoelectric means to give a signal thereto for a zero electric current to said motor means when said reflected beam is coincident with a predetermined path and a current of selected phase to said motor means for returning said reflected beam to said predetermined path when said reflected beam moves away therefrom, linkage means for flexibly holding said prism with said apex centered under the ram while the tube is transversed thereunder by the carriage, a chart movable with the carriage, and stylus means electrically responsive to movement of said pentaprism for recording on said chart any deviation in the bore along the vertical plane.

References Cited in the file of this patent UNITED STATES PATENTS 1,564,432 Marcuse et a1. Dec. 8, 1925 2,703,505 Senn Mar. 8, 1955 FOREIGN PATENTS 284,120 Switzerland July 15, 1952 

